1. Field of the Invention
The present invention relates to a hinge construction for a split-type seat back, which is disposed between right and left seat backs.
2. Description of Related Art
Some vehicular rear seats are of a type such that a seat back is divided into right and left. Such a split-type seat back is arranged so that each seat back can be reclined-forward via a center hinge etc. In a hinge construction for such a seat back, a mounting bracket is installed at a side of each of the seat backs divided into right and left, and a center hinge bracket is installed on the vehicle body floor side. By inserting a connecting pin in hinge holes of the mounting bracket and the center hinge bracket, the right and left seat backs can be reclined while being connected to each other (for example, see Patent Document 1).    [Patent Document 1] Japanese Patent Provisional Publication No. 9-226426 (No. 226426/1997)
Also, in the split-type seat back, the seat back is divided in a ratio of 6:4 to improve seat comfort of a passenger seated in the center. The split-type seat back in which the right and left seat backs have a different width has become mainstream. For the seat back of this type, when a load is applied from the outside, a high moment load is applied to a hinge portion of the wider seat back, which is formed at the ratio of 6.
A center hinge portion provided between the right and left seat backs (at the boundary position) must have a sufficient strength because it supports the right and left seat backs that recline forward. In order to increase the strength of the center hinge portion, it is preferable that a connecting pin be directly fastened to a frame of the seat back by inserting the connecting pin in a hinge hole in a center hinge bracket and in the frame of the seat back without the use of a mounting bracket.
However, in the hinge construction in which the connecting pin is directly fastened to the frame of the seat back, since the center hinge portion is provided between the right and left seat backs, parts are unable to be laid out, or installation work must be done in a tight space for the reason that a tightening tool cannot be inserted depending on the construction of the center hinge portion or for other reasons, which presents a problem in that work efficiency cannot be improved.